Nikkei suffers longest losing streak since November

* Nikkei falls 0.8 pct to one-week low, Topix slips 0.4 pct * Toyota falls after weak U.S. auto sales in April * Sharp gains on report of potential $1 bln credit line * Japanese markets closed for holidays Friday, Monday By Dominic Lau TOKYO, May 2 (Reuters) - Japan's Nikkei average fell for a fourth straight session on Thursday, its worst losing streak since November, just before Prime Minister Shinzo Abe began promising to revive growth, dubbed as "Abenomics" that has spur